BATH, Maine — Bath Iron Works on Thursday confirmed that the company would lay off 40 employees effective Sept. 6.

The layoffs — 15 pipe coverers and 25 insulators — are due to a lack of work for those particular trades, BIW spokesman Jim DeMartini said. Specific employees will be notified next week.

“The layoffs [Thursday] reflect the typical fluctuation we see for specific trades throughout the course of the production cycle,” he said. “We’re always looking to balance the work we have with the resources.”

In June, when the Navy announced contracts for the four new DDG-51s, Dan Dowling, president of Local S6 of the machinists union — which represents 3,000 BIW workers — said he had hoped BIW would be awarded five ships instead of four with the option for a fifth, but that the announcement indicated employment would be more stable in the future.

“It will provide us a little more security for the future,” he said. “Things have been looking up compared to where we were a year or so ago. It should keep the employment levels stable. The company has been doing some hiring, so we’ve been gearing up. Things are moving in the right direction.”

Dowling did not immediately return a call for comment on Thursday.

U.S. Sen. Susan Collins, a member of the Senate Defense Appropriations Subcommittee, said in July that she hoped to secure funding for the fifth ship in the defense budget bill. She said funding for the ship would “help keep BIW employees building ships and will avoid hundreds of layoffs that otherwise would have occurred.”

DeMartini said a fluid workforce is characteristic of the shipbuilding business.

“It’s just a cycle of what work is being done in various stages of construction, that at the moment doesn’t require that number of people to do what must be done,” he said.

DeMartini said he was not sure when the company last laid people off, but he noted that since the beginning of 2013, the company has added 370 new employees and recalled an additional 125 employees who were previously laid off during that time.